JP5458271B2 - Dye-sensitized solar cell and method for producing the same - Google Patents

Description

  The present invention relates to a dye-sensitized solar cell and a method for producing the same.

The dye-sensitized solar cell is called a wet solar cell or a Gretzel battery, and is characterized in that it has an electrochemical cell structure typified by an iodine solution without using a silicon semiconductor. Specifically, a porous semiconductor layer such as a titania layer formed by baking a titanium dioxide powder or the like on a transparent conductive glass plate (transparent substrate on which a transparent conductive film is laminated) and adsorbing a pigment thereto, and conductive glass It has a simple structure in which an iodine solution or the like is disposed as an electrolytic solution between counter electrodes made of a plate (conductive substrate). Electrons are generated by the absorption of sunlight into the dye-sensitized solar cell from the transparent conductive glass plate side.
Dye-sensitized solar cells are attracting attention as low-cost solar cells because they are inexpensive and do not require large-scale equipment for production.

Dye-sensitized solar cells are required to further improve the conversion efficiency of sunlight, and have been studied from various viewpoints.
As one of them, in order to improve the power extraction efficiency by improving the conductivity of the electrode, it has been studied to omit the transparent conductive film normally formed on the transparent substrate provided on the light incident side. Improvement of the conductivity of the electrode is particularly significant when the size of the solar cell is increased.

As such a technique, for example, a photoelectric conversion element having a structure including a laminated portion including a semiconductor fine particle layer, a metal network, a charge transfer layer, and a counter electrode in this order on a glass substrate is disclosed (Patent Documents 1 and 2). reference).
In addition, for example, by providing a transparent conductive film and a mesh-shaped conductor made of a metal or alloy having a lower resistance value than the transparent conductive film on the substrate, the resistance of the electrode is reduced, and further, the mesh shape In order to prevent an increase in the resistance value caused by oxidation of the conductor, a dye-sensitized solar cell in which a passive film is formed on the surface of the mesh-like conductor and a film such as a semiconductor film is further formed thereon An electrode is disclosed (see Patent Document 3).

  Also, for example, a dye-sensitized solar cell having SUS as a collector electrode on a transparent substrate, a SiOx film widely used as an insulator on SUS, and an SUS electrode sputtered with ITO on the SiOx film. Is disclosed (see Non-Patent Document 1). The solar cell conversion efficiency of this solar cell is reported to be 4.2%.

  Various techniques have been disclosed in which the counter electrode is formed of a conductive transparent substrate and light is introduced into the dye-sensitized solar cell from the counter electrode side (see, for example, Patent Document 4).

JP 2001-283941 A JP 2007-73505 A JP 2005-197176 A Japanese Patent No. 2664194

Kang-Jin Kim, et al., A4.2% efficient flexible dye-sensitized TiO2 solar cells using stainlesssteel substrate, Solar Energy Materials & Solar Cells 90 (2006) 574-581

  However, any of the above-described conventional techniques needs further improvement in order to further improve the power extraction efficiency.

  This invention is made | formed in view of said subject, and it aims at providing the dye-sensitized solar cell which can aim at the further improvement of electric power taking-out efficiency, and its manufacturing method.

The dye-sensitized solar cell according to the present invention has a substrate, a conductive substrate serving as a cathode electrode, and is disposed between the substrate and the conductive substrate in the vicinity of or in contact with the substrate to adsorb the dye. A porous semiconductor layer, and a conductive metal layer disposed in contact with the porous semiconductor layer and serving as an anode, wherein at least one of the substrate and the conductive substrate is a transparent substrate, and the electrolyte is A sealed dye-sensitized solar cell,
The conductive metal layer is composed of a conductive metal portion and a covering portion that is coated on at least a side of the conductive metal portion in contact with the porous semiconductor layer,
The coating portion, and having a gradient composition structure oxidation degree increases toward the side of the conductive metal portion on a side of the porous semiconductor layer.

  In the dye-sensitized solar cell according to the present invention, preferably, the covering portion is an oxide of one or more types of corrosion-resistant metal materials selected from the group consisting of Ti, W, Ni, Pt and Au. It is formed.

  In the dye-sensitized solar cell according to the present invention, preferably, the conductive metal layer is a current collector disposed on the side of the porous semiconductor layer opposite to the side on which the substrate is provided, Innumerable holes for allowing the electrolyte to freely flow through the porous semiconductor layer are formed in the conductive metal portion and electrically connected to external electrodes, and the substrate is a transparent substrate. Features.

  The dye-sensitized solar cell according to the present invention is preferably characterized in that the conductive metal portion of the conductive metal layer is a mesh member.

  In the dye-sensitized solar cell according to the present invention, preferably, the conductive metal layer is a current collector provided on a surface of the substrate, and the conductive metal portion is provided on a side in contact with the substrate. In addition, the conductive metal portion is covered to provide the covering portion, and the conductive substrate is a transparent substrate.

Moreover, the dye-sensitized solar cell according to the present invention is a method for producing the above-described dye-sensitized solar cell,
In the step of forming the covering portion on the conductive metal portion formed in advance, while introducing a small amount of a compound containing one or more elements selected from the group consisting of O, N, S, P, B and C A gradient composition structure is formed by depositing a conductive metal-coated raw metal by a thin film technique.

Moreover, the dye-sensitized solar cell according to the present invention is a method for producing the above-described dye-sensitized solar cell,
In the step of forming a covering portion on a conductive metal portion that has been formed in advance, a gradient composition structure is provided by including a step of forming a sputter layer by a sputtering method and a step of forming a vapor deposition layer on the surface of the sputter layer by a vacuum vapor deposition method. It is characterized by forming.

  In the dye-sensitized solar cell according to the present invention, preferably, the vacuum vapor deposition method is an arc plasma vapor deposition method or a vacuum arc vapor deposition method.

In the dye-sensitized solar cell according to the present invention, the conductive metal layer disposed in contact with the porous semiconductor layer and serving as the anode electrode is in contact with the conductive metal portion and at least the porous semiconductor layer of the conductive metal portion. It has a gradient composition structure in which the degree of oxidation increases from the conductive metal part side to the porous semiconductor layer side, so that high power extraction efficiency is obtained. Can do.
In addition, the method for producing a dye-sensitized solar cell according to the present invention is selected from the group consisting of O, N, S, P, B, and C in the step of covering the conductive metal portion formed in advance with the covering portion. Since a gradient composition structure is formed by forming a film by thin film technology while introducing a small amount of a compound containing one or two or more elements, the dye-sensitized solar cell according to the present invention can be suitably obtained.

It is a schematic diagram of the cross-section of the dye-sensitized solar cell which concerns on the 1st example of this Embodiment. It is a figure for demonstrating the electroconductive metal layer comprised by the electroconductive metal part formed with a mesh member, and the coating | coated part coat | covered with an electroconductive metal part. It is a figure for demonstrating the electroconductive metal layer comprised by the sheet-like electroconductive metal part previously punched and the coating | coated part coat | covered with an electroconductive metal part. It is a schematic diagram of the cross-section of the dye-sensitized solar cell which concerns on the 2nd example of this Embodiment. It is a figure for demonstrating an example of the manufacturing method of the dye-sensitized solar cell of this Embodiment. It is a figure for demonstrating another example of the manufacturing method of the dye-sensitized solar cell of this Embodiment. It is a figure for demonstrating the preparation methods of a dye-sensitized solar cell. It is a figure which shows the SEM surface observation result of the layer used as a coating | coated part, (a) is the application | coating method of a prior art, (b) is the sputtering method of this Embodiment, (c) is the arc of this Embodiment. Each film is formed by plasma deposition.

    Preferred embodiments of a dye-sensitized solar cell and a method for producing the same according to the present invention will be described below with reference to the drawings.

The inventors of the present invention have studied various reasons for the low power extraction efficiency of the above-described conventional dye-sensitized solar cells.
In the prior art, when a titania paste is applied to a low-resistance conductive metal coated with a protective film for preventing oxidative corrosion instead of a transparent conductive film and then sintered, for example, the coefficient of thermal expansion (linear expansion) A stainless material having a rate of about 16 × 10 ⁻⁶ / ° C. is used as the conductive metal. At this time, since the difference in thermal expansion between the conductive metal and the titania fired layer having a thermal expansion coefficient of about 5 × 10 ⁻⁶ / ° C. is large, it is caused by the difference in thermal expansion coefficient during heating or cooling during titania firing. The shearing force generated between the conductive metal and the titania fired layer due to the difference in the expansion coefficient and shrinkage between the conductive metal and the titania fired layer results in partial peeling of the protective film and the effect of the protective film is impaired. As a result, it has been thought that photoelectric conversion efficiency may not be sufficiently obtained.
And, in order to improve the above-mentioned problems, the side close to the conductive metal is formed of a material close to the thermal expansion coefficient of the conductive metal and the side close to the titania fired layer is titania fired. It was conceived that the layer is made of a material having a thermal expansion coefficient close to that of the layer.

That is, the basic principle of the dye-sensitized solar cell according to the present embodiment is as follows.
The dye-sensitized solar cell includes a substrate, a conductive substrate serving as a cathode electrode, a porous semiconductor layer that is disposed between or in contact with the substrate, adsorbs the dye, and porous A conductive metal layer disposed in contact with the porous semiconductor layer and serving as an anode electrode. At least one of the substrate and the conductive substrate is a transparent substrate, and an electrolyte is sealed in the dye-sensitized solar cell.
The conductive metal layer includes a conductive metal portion and a covering portion that covers at least a side of the conductive metal portion that contacts the porous semiconductor layer. The covering portion has a gradient composition structure in which the coefficient of thermal expansion decreases from the conductive metal portion side toward the porous semiconductor layer side.
With the above configuration, even if shear force is generated between the conductive metal part and the titania fired layer due to the difference in expansion coefficient and shrinkage rate between the conductive metal part and the porous semiconductor layer (titania fired layer), The applied stress is alleviated, cracks are generated in the covering portion, and the phenomenon that the covering portion is peeled off from the conductive metal portion is reduced. Thereby, the function of the covering portion is maintained without being impaired, and high power extraction efficiency (conversion efficiency) can be obtained.

First, the dye-sensitized solar cell which concerns on the 1st example of this Embodiment is demonstrated with reference to the schematic diagram of FIG.
The dye-sensitized solar cell 10 according to the first example of the present embodiment includes a substrate 12 and a porous semiconductor layer 14 that adsorbs a dye disposed on the substrate 12 (downward in FIG. 1; the same applies hereinafter). And a conductive metal layer 16 disposed on the surface of the porous semiconductor layer 14 opposite to the transparent substrate 12, and a conductive substrate 18 provided to face the substrate 12.
An internal spacer 21 (support) is provided between the conductive metal layer 16 and the conductive substrate 18. An electrolyte (electrolytic solution) 22 is filled in the space of the dye-sensitized solar cell 10 sealed with the spacer 20.
The substrate 12 is a transparent substrate, and incident light is introduced into the cells of the dye-sensitized solar cell 10 from the substrate 12 side.
As shown in FIG. 1, the porous semiconductor layer 14 may be disposed in contact with the substrate 12, or may be disposed in proximity to the substrate 12.
The conductive metal layer 16 is electrically connected to the external electrode 26. The external electrode 26 may be provided at an appropriate position independently of the substrate 12.
The conductive substrate 18 includes a substrate 28, a transparent conductive film 30 formed on the substrate 28, and a catalyst film (catalyst layer) 32 formed on the transparent conductive film 30. However, the present invention is not limited to this, and an appropriate configuration that is normally employed may be employed.
The internal spacer 21 is provided in order to more reliably perform electrical insulation between the conductive metal layer 16 and the conductive substrate 18. The inner spacer 21 can be made of, for example, a spherical material having a diameter of about 20 μm formed of a zirconia material, a non-woven fabric made of resin or glass that is insoluble in the electrolytic solution, and the like. However, the inner spacer 21 is not necessarily provided as long as the conductive metal layer 16 and the conductive substrate 18 are reliably spaced apart and insulated by the spacer 20.

The substrate 12 and the substrate 28 may be glass plates or plastic plates, for example. When using a plastic plate, for example, PET, PEN, polyimide, a cured acrylic resin, a cured epoxy resin, a cured silicone resin, various engineering plastics, a cyclic polymer obtained by metathesis polymerization, and the like can be given.
The transparent conductive film 30 may be, for example, ITO (indium film doped with tin), FTO (tin oxide film doped with fluorine), or SnO ₂ film. .
As the catalyst film 32, a platinum film, highly conductive carbon, or the like can be used.

The porous semiconductor layer 14 is baked at a temperature of 300 ° C. or higher, and more preferably baked at a temperature of 450 ° C. or higher. On the other hand, although there is no particular upper limit on the firing temperature, the temperature is sufficiently lower than the melting point of the material of the porous semiconductor layer 14, and more preferably 550 ° C. or less.
The thickness of the porous semiconductor layer 14 is not particularly limited, but is preferably 14 μm or more.

  The dye adsorbed on the porous semiconductor layer 14 is a dye adsorbed on the semiconductor material forming the porous semiconductor layer 14 and has absorption at a wavelength of 400 nm to 1000 nm. Examples of such a dye include a metal complex having a COOH group such as a ruthenium dye and a phthalocyanine dye, and an organic dye such as a cyanine dye. A plurality of dyes having different light absorption regions may be mixed and adsorbed on the porous semiconductor layer 14, or a plurality of different dyes may be adsorbed in layers.

  The electrolyte 22 contains iodine, lithium ions, ionic liquid, t-butylpyridine, and the like. For example, in the case of iodine, an oxidation-reduction body composed of a combination of iodide ions and iodine can be used. The redox form contains an appropriate solvent that can dissolve the redox form.

The conductive metal layer 16 is a current collector disposed on the side of the porous semiconductor layer 14 opposite to the side on which the substrate 12 is provided. As shown in FIG. 2, the conductive metal layer 16 includes a conductive metal portion 17 and a covering portion 19 that is covered with the conductive metal portion 17. The covering portion 19 includes an inner layer 19a and an outer layer 19b. In the conductive metal layer 16, innumerable holes 24 for allowing the electrolyte 22 to freely flow through the porous semiconductor layer 14 are formed in the conductive metal portion 17.
The conductive metal portion 17 shown in FIG. 2 is a mesh member. The covering portion 19 covers the entire surface of the conductive metal portion 17 by a film forming method to be described later. However, the present invention is not limited to this, and if the corrosion resistance of the conductive metal portion 17 is not so much required, the covering portion 19 is necessary. Thus, at least the side of the conductive metal portion 17 that contacts the porous semiconductor layer 14 may be covered. The same applies to other embodiments described below.
The covering portion 19 has a gradient composition structure in which the degree of oxidation increases from the conductive metal portion 17 side toward the porous semiconductor layer 14 side. This gradient composition structure may be one in which the composition changes continuously, or one in which the composition changes stepwise (stepwise). That is, the covering portion 19 may have a single-layer structure in which the degree of oxidation is gradually changed from the inside toward the outside during film formation. In addition, two or more materials having different degrees of oxidation were used, and the inner layer on the conductive metal portion 17 side was formed of a material having a low degree of oxidation, and the outer layer on the porous semiconductor layer 14 side was formed of a material having a high degree of oxidation. A multilayer structure composed of different material layers may be used.
In the case of the covering portion 19 of FIG. 2, the degree of oxidation of the outer layer 19b is higher than that of the inner layer 19a.
The thickness of the conductive metal portion 17 is not particularly limited, and can be, for example, about several tens of nm to several tens of μm. From the viewpoint of obtaining a low electric resistance (resistance), the thickness is about several μm to about 10 μm. It is appropriate and sufficient.
The thickness of the covering portion 19 is not particularly limited, and can be, for example, about several hundred nm. When the thickness is at least 20 nm or more, the reverse electron transfer from the conductive metal layer 16 to the electrolyte 22 is prevented, and It is more preferable at the point which can relieve | moderate the difference with the thermal expansion coefficient with the electroconductive metal part 17. FIG.

As long as the conductive metal portion 17 has moderate conductivity, an appropriate metal can be selected and used. For example, metals such as Ti, Pt, Au, and Ag, alloys thereof, and metal oxides can be used. Metal compounds such as stainless steel, iron, copper, aluminum, tin, and the like can be used. Of these, it is more preferable to use stainless steel from the viewpoint of cost reduction of the material and higher conductivity.
The covering portion 19 is preferably made of a corrosion-resistant metal, and more preferably an oxide of one or more types of corrosion-resistant metal materials selected from the group consisting of Ti, W, Ni, Pt and Au.

Instead of the conductive metal layer 16 in FIG. 2, a conductive metal layer 16a having a conductive metal portion 17a as shown in FIG. 3 may be used.
The conductive metal layer 16a is, for example, a sheet-like conductive metal portion 17a that has been punched in advance, and the conductive metal portion 17a is covered with a covering portion 19. In this case, holes having a desired size, shape and arrangement can be formed.

In the dye-sensitized solar cell 10 according to the first example of the present embodiment configured as described above, the covering portion 19 is directed from the conductive metal portions 17 and 17a toward the porous semiconductor layer 14. By having a graded composition structure in which the degree of oxidation is high, the graded composition structure has a thermal expansion coefficient that decreases from the conductive metal portion 17 side toward the porous semiconductor layer 14 side. That is, the inner layer 19 a of the covering portion 19 has a high coefficient of thermal expansion close to that of the conductive metal portion 17, and the outer layer 19 b of the covering portion 19 has a low coefficient of thermal expansion close to that of the porous semiconductor layer 14.
In addition, the gradient composition structure of the covering portion 19 in which the coefficient of thermal expansion decreases from the conductive metal portion 17 side toward the porous semiconductor layer 14 side uses, for example, materials having two or more different thermal expansion coefficients, It can also be obtained by forming the metal portion 17 side with a material having a high coefficient of thermal expansion and forming the porous semiconductor layer 14 side with a material having a low coefficient of thermal expansion.
As a result, the dye-sensitized solar cell 10 has a phenomenon that a crack occurs in the covering portion due to a severe temperature change at the time of manufacture, and further the phenomenon that the covering portion peels from the conductive metal portion or the conductive metal covered portion and the porous semiconductor layer By reducing the phenomenon of separation, the function of the covering portion is maintained without being impaired, and good adhesion between the porous semiconductor layer and the conductive metal layer is maintained, and high power extraction efficiency can be obtained. .
In addition, since a process of forming a porous semiconductor layer 14 by firing a titania paste disposed on the substrate 12 is usually employed, it is necessary to use a glass substrate as the substrate 12 in order to withstand a high temperature exceeding 450 ° C., for example. . On the other hand, the dye-sensitized solar cell 10 can join the conductive metal layers 16 and 16a on which the porous semiconductor layer 14 is placed to the substrate 12 at the time of cell assembly. Any plastic material can be used.
In the dye-sensitized solar cell 10, electrons easily move in the porous semiconductor layer 14 through the conductive metal layer 16, and further, reverse electron transfer at the interface between the conductive metal layer 16 and the electrolyte 22. Is unlikely to occur.
Moreover, since the dye-sensitized solar cell 10 does not use a glass substrate with a transparent conductive film, an inexpensive substrate 12 can be used.
Moreover, the dye-sensitized solar cell 10 can obtain better adhesion between the covering portion and the porous semiconductor layer by appropriately selecting the material of the covering portion or adjusting the film forming conditions.
Further, the dye-sensitized solar cell 10 is obtained by applying a conductive metal layer 16 with a porous semiconductor layer 14 obtained by applying a titania paste to a conductive metal layer 16 and baking the conductive substrate 18 and a plastic made of, for example, Ti foil. Since it can be produced by being sandwiched between substrates 12 made of a sheet, it can be mass-produced at low cost by adopting a so-called roll-to-roll method.

Next, a dye-sensitized solar cell according to a second example of the present embodiment will be described with reference to the schematic diagram of FIG.
Since the approximate configuration of the dye-sensitized solar cell 10a according to the second example of the present embodiment is the same as that of the dye-sensitized solar cell 10, description of overlapping components is omitted. Moreover, since it is the same as that of the dye-sensitized solar cell 10 except what mentions especially below also about an effect, the description of the overlapping effect is abbreviate | omitted.

The dye-sensitized solar cell 10a is provided with a counter electrode so that the substrate 12a and the conductive metal layer (hereinafter referred to as reference numeral 23) can be integrally provided prior to the assembly of the solar cell so that the number of constituent members can be reduced. The point which introduce | transduces incident light into a cell from the side of a certain conductive substrate 18 differs greatly from the dye-sensitized solar cell 10. FIG.
In order to realize the above structure, a transparent substrate is used as the conductive substrate 18. The substrate 12a may be a transparent substrate or an opaque substrate. The conductive metal layer 23 is a current collector provided on the surface of the substrate 12a. A sheet-like conductive metal portion 23a is provided on the side in contact with the substrate 12a, and the conductive metal portion 23a is further covered to form a sheet. The covering portion 23b is provided.
As long as the conductive metal layer 23 has a certain rigidity, the substrate 12a can be omitted. Further, it is not excluded to use a mesh member as the conductive metal portion 23a on the assumption that the substrate 12a exists.

  Next, with respect to the method for producing the dye-sensitized solar cell of the present embodiment, in which the dye-sensitized solar cell of each example of the present embodiment can be suitably produced, the schematic diagrams of FIGS. 5 and 6 are used. The description will be given with reference.

A manufacturing method will be described by taking the dye-sensitized solar cell 10 as an example.
The conductive metal portion 17 of the conductive metal layer uses the mesh member (wire net) shown in FIG. In addition, also when using the electroconductive metal layer of the perforated sheet | seat of FIG. 3 as an electroconductive metal layer, the following process does not change. For convenience of explanation, the process for producing the conductive metal layer will be described later, and the process for producing the dye-sensitized solar cell using the produced conductive metal layer will be described first. This process is the same as the process for producing a conventional dye-sensitized solar cell.

As shown in FIG. 5, for example, titania paste is applied on the produced conductive metal layer 16 and baked at a temperature of 450 ° C., for example, to form the porous semiconductor layer 14 on the conductive metal layer 16.
Next, the conductive metal layer 16 with the porous semiconductor layer 14 is impregnated in the dye solution for 48 hours, for example, and the dye is attached to the porous semiconductor layer 14.

Next, as shown in FIG. 6, the conductive substrate 18 having a porous semiconductor layer 14 to which a dye is attached is prepared using a separately manufactured conductive substrate 18 made of a substrate with a transparent conductive film and a catalyst film, and a separately manufactured substrate 12. A cell is assembled using a spacer (not shown) so as to sandwich the metal layer 16, and an electrolyte is injected into the cell to produce a dye-sensitized solar cell. In this case, if the porous plastic sheet impregnated with the electrolytic solution is arranged between the conductive metal layer 16 with the porous semiconductor layer 14 and the conductive substrate 18 attached with the dye, the electrolytic solution is obtained after the cell is completed. This is suitable for adopting the roll-to-roll method described above.
In addition, when producing the dye-sensitized solar cell 10a, as shown in FIG. 7, the sheet-like conductive metal layer 16 is formed on the substrate 12 by a thin film technique, and the substrate 12 with the conductive metal layer 16 is formed. Next, the porous semiconductor layer 14 is formed on the conductive metal layer 16 by, for example, applying a titania paste on the substrate 12 with the conductive metal layer 16 and baking it at a temperature of 450 ° C., for example. Is the same as the above manufacturing method. Here, in FIG. 7, for convenience of illustration, the conductive metal layer 16 and the substrate 12 are shown separately, but in reality, the conductive metal layer 16 is formed in close contact with the substrate 12. Just as you did.

  Next, a method for producing a conductive metal layer will be described.

In the case of the dye-sensitized solar cell 10, a small amount of a compound containing one or more elements selected from the group consisting of O, N, S, P, B, and C is introduced into a conductive metal part such as a mesh member. However, by forming a raw material metal of the covering portion by thin film technology, a covering portion having a graded composition structure of the degree of oxidation, that is, the coefficient of thermal expansion, is formed on the conductive metal portion. The element to be introduced is more preferably O or N.
On the other hand, in the case of the dye-sensitized solar cell 10a, a sheet-like conductive film which is a conductive metal portion is formed on a substrate, and then a sheet-like covering portion is formed on the conductive film in the same manner as described above. Form.
In addition, as described above, the gradient composition structure may be formed using materials having two or more different thermal expansion coefficients, and moreover, two or more stages of film formation using the same material and different film formation methods. By performing the step, two or more layers having different coefficients of thermal expansion may be formed.
For example, when forming a film using Ti as a raw metal, the thermal expansion coefficient of the porous semiconductor layer 14 is 5 × 10 ⁻ by making the covering portion on the porous semiconductor layer 14 side have a structure close to TiO ₂ having a high degree of oxidation. ^The thermal expansion coefficient is close to 8.4 × 10 ⁻⁶ / ° C. with a coefficient of thermal expansion close to ⁶ / ° C., while the coating portion on the conductive metal portion 17 side has a structure close to Ti having a low degree of oxidation. Rate.
In addition, in order to measure the value of a thermal expansion coefficient and an oxidation degree as needed, an appropriate method can be used.
Regarding the degree of oxidation, for example, using Auger electron spectroscopy (scanning type Auger electron spectrometer ULVAC PHI-700), the degree of oxidation is calculated from the ratio of the peak intensity of the standard metals and oxygen to the peak intensity of the sample. can do.
Regarding the coefficient of thermal expansion, for example, the coefficient of thermal expansion corresponding to the degree of oxidation obtained by measuring the degree of oxidation can be calculated from the values described in the Metal Handbook 5th edition (Maruzen).

The thin film technique for forming the covering portion is not particularly limited, but preferably a sputtering method or a vacuum evaporation method is used.
At this time, the covering portion having the gradient composition structure can be formed using only one of these methods. Preferably, the method includes a step of forming a sputter layer on the surface of the conductive metal portion by a sputtering method and a step of forming a vapor deposition layer on the surface of the sputter layer by a vacuum vapor deposition method.
The aggregate of fine metal particles in the outer layer formed by the vacuum deposition method is smaller in size than the fine metal particles in the inner layer of the covering portion formed by the sputtering method. This also contributes to the favorable formation of a gradient composition structure having a large composition change. In addition, the film thickness of the vapor deposition layer is greatly increased during the subsequent firing, which means that the oxidation in the vapor deposition layer has sufficiently progressed during firing and that the vapor deposition layer cracks during firing. This is considered to indicate that it contributes to mitigation.
It is more preferable that the vacuum vapor deposition method is an arc plasma vapor deposition method (plasma arc deposition method) or a vacuum arc vapor deposition method because the flatness is excellent and a denser coating portion can be obtained.

In FIG. 8, the SEM surface observation result of the layer used as the coating part after baking for 30 minutes at 450 degreeC is shown. In FIG. 8, (a) shows a film formed by a conventional coating method, (b) shows a film formed by a sputtering method of this embodiment, and (c) shows a film formed by an arc plasma vapor deposition method of this embodiment. . As an example of flatness, (a) the surface roughness Ra of the film formed by the coating method is 5.28 nm, and (b) the surface roughness Ra of the film formed by the sputtering method of the present embodiment is 1.96 nm. (C) The surface roughness Ra of the film formed by the arc plasma deposition method of the present embodiment was 0.55 nm.
Moreover, although illustration is omitted, according to SEM observation, when a porous semiconductor layer is formed on a stainless steel mesh that is not covered with a coating part, a clear crack occurs in the stainless steel mesh, and the coating part formed by a coating method is used. In the case where a porous semiconductor layer is formed on a coated stainless steel mesh, cracks are observed in the coated portion or the stainless steel mesh and unevenness of the porous semiconductor layer is observed. In the case where the porous semiconductor layer was formed on the stainless mesh coated with the laminated coating portion, no crack was observed, and it was observed that the porous semiconductor layer was uniformly formed on the stainless mesh.
Although the data is omitted, the contact angle was measured, and compared with the stainless steel mesh coated with the coating formed by the coating method, it was coated with the coating formed by the sputtering method and the arc plasma deposition method of this embodiment. Large values were obtained for the stainless steel mesh.

  The present invention will be further described with reference to examples and comparative examples. In addition, this invention is not limited to the Example demonstrated below.

(Stainless steel mesh used)
Stainless steel mesh # 500 (wire diameter: 0.025 mm, opening (opening, opening): 0.026 mm, space ratio: 25.8%, thickness: 55 μm, material: SUS316) was used.

Example 1
A sputtering film having a thickness of 200 nm was formed on both surfaces of a 40 mm × 50 mm stainless steel mesh by using Ti as a raw material metal and processing by sputtering at an output of 250 W for 50 minutes. At this time, a small amount of oxygen gas was introduced and circulated through the film forming apparatus having a chamber internal pressure of 2.0 × 10 ⁻⁴ Pa, and the chamber internal pressure was maintained at 4.0 × 10 ⁻⁴ Pa.
After the formed stainless steel mesh was cut into 20 mm × 25 mm, a TiO ₂ paste for screen printing (Ti-Nanoxide D / SP) manufactured by Solaronix SA was applied by a squeegee method using a metal mask (20 mm × 5 mm). Then, it baked for 30 minutes at the temperature of 450 degreeC with the electric furnace. After cooling, it was immersed in a dye (N719) solution for 48 hours, then rinsed thoroughly with a mixed solution of acetonitrile and t-butyl alcohol (1: 1 (v / V)), then cut to 25 mm × 5 mm, A conductive metal layer on which a porous semiconductor layer having a dye attached was placed was obtained.
On the other hand, a polyethylene porous film manufactured by Nippon Sheet Glass Co., Ltd. (film thickness 40 μm, space ratio 80%) cut into 15 mm × 10 mm is coated with an organic solvent electrolyte (LiI 500 mM, I ₂ 50 mM, t-Bupy 580 mM, MeEtImN (CN) ₂ A porous film was produced by immersing 600 mM in Acetonitorile), and a platinum sputtered Ti counter electrode (platinum sputter output 200 W / 50 min, Ti plate thickness 3 mm) was produced.
On the opposite side of the conductive metal layer from the side on which the porous semiconductor layer is placed, a porous film and a platinum sputter counter electrode are stacked in this order, and are cut into 26 mm × 10 mm micro slide glass manufactured by MASHNAMI (S1127,
A solar cell was obtained by sealing with epoxy resin in a state of being sandwiched from two sides with a thickness of 1.2 mm.
The performance evaluation of the obtained solar battery cell was performed using a solar simulator (dye-sensitized spectral sensitivity measuring device KHP-1 type) manufactured by Spectrometer Co., Ltd.
The performance evaluation results are shown in Table 1. In Table 1, efficiency indicates conversion efficiency, FF indicates fill factor, V _OC indicates optical open circuit voltage, and _JSC indicates optical short circuit current density. The results of performance evaluation of other examples and comparative examples below are also shown in Table 1.

(Example 2)
A solar cell was produced in the same manner as in Example 1 except that the stainless steel mesh was covered with an arc plasma film formed by an arc plasma deposition method instead of the sputtered film, and performance evaluation was performed.
In the arc plasma deposition method, a small amount of oxygen gas was introduced into the chamber of the film forming apparatus, and an arc plasma film having a film thickness of 100 mm was formed with 2000 shots while maintaining the chamber internal pressure at 4.0 × 10 ⁻⁴ Pa.

(Example 3)
Except for coating the stainless steel mesh with the sputtered film under the conditions of Examples 1 and 2 and further with the arc plasma film, solar cells were produced in the same manner as in Example 1 and performance evaluation was performed.

Example 4
Instead of the stainless steel mesh, a porous Ti foil having a hole diameter of 75 μm and a hole thickness of 150 μm was drilled with an NC drill and having a thickness of 20 μm was coated with an arc plasma film formed by an arc plasma deposition method. Other than that, solar cells were produced in the same manner as in Example 1, and performance evaluation was performed.

(Example 5)
A sputtered film having a film thickness of 300 nm was formed on both surfaces of a 40 mm × 50 mm stainless steel mesh by using W as a raw material metal and by sputtering at an output of 200 W for 60 minutes. At this time, a small amount of oxygen gas was introduced and circulated through the film forming apparatus having a chamber internal pressure of 2.5 × 10 −4 Pa to maintain the chamber internal pressure at 4.0 × 10 −4 Pa.
After the formed stainless steel mesh was cut into 20 mm × 25 mm, a TiO 2 paste for screen printing (Ti-Nanoxide D / SP) manufactured by Solaronix SA was applied by a squeegee method using a metal mask (20 mm × 5 mm). Then, it baked for 60 minutes at the temperature of 450 degreeC with the electric furnace. After cooling, soak in a dye (black dye) solution for 24 hours, and then rinse thoroughly with a mixed solution of acetonitrile and t-butyl alcohol (1: 0.9 (v / V)), then cut to 25 mm x 5 mm Thus, a conductive metal layer on which the porous semiconductor layer to which the dye was attached was placed was obtained.
On the other hand, an organic solvent electrolyte (LiI 500mM, I2 50mM, t-Bupy 580mM, MeEtImN (CN) ₂ 600mM) on a polyethylene porous film (film thickness 40μm, porosity 80%) manufactured by Nippon Sheet Glass Co., Ltd. cut to 15mm x 10mm , in Acetonitorile) to prepare a porous film, and a platinum sputtered Ti counter electrode (platinum sputter output 250 W / 50 min, Ti plate thickness 4 mm).
A microslide glass (S1127, thickness: 1.1) made of MATSNAMI, which was cut into a size of 26 mm × 10 mm, in which a porous film and a platinum sputter counter electrode were stacked in this order on the side opposite to the side on which the porous semiconductor layer of the conductive metal layer was placed. 2 mm) In a state of being sandwiched by two sheets from both sides, it was sealed with an epoxy resin to obtain a solar battery cell.
The performance evaluation of the obtained solar battery cell was performed in the same manner as in Example 1.

(Comparative Example 1)
Except using the stainless steel mesh which does not form into a film, the solar cell was produced by the method similar to Example 1, and performance evaluation was performed.

(Comparative Example 2)
A solar battery cell was produced by the same method as in Example 1 except that a stainless steel mesh was coated with a TiO ₂ film having a thickness of 200 nm by a coating method, and performance evaluation was performed.

(Comparative Example 3)
A solar battery cell was produced in the same manner as in Example 4 except that the porous Ti foil without film formation was used as it was, and performance evaluation was performed.

10 Dye-sensitized solar cell 12, 28 Substrate 14 Porous semiconductor layer 16, 16a, 23 Conductive metal layer 17, 17a, 23a Conductive metal portion 18 Conductive substrate 19, 23b Cover portion 19a Inner layer 19b Outer layer 21 Internal spacer 20 Spacer 22 Electrolyte 23a Conductive metal part 26 External electrode 30 Transparent conductive film 32 Catalyst film

Claims (8)

A substrate, a conductive substrate to be a cathode, a porous semiconductor layer that is disposed between the substrate and the conductive substrate in the vicinity of or in contact with the substrate, and adsorbs a dye; and the porous semiconductor layer A dye-sensitized solar cell comprising a conductive metal layer disposed in contact with the anode and serving as an anode, wherein at least one of the substrate and the conductive substrate is a transparent substrate, and an electrolyte is sealed There,
The conductive metal layer is composed of a conductive metal portion and a covering portion that is coated on at least a side of the conductive metal portion in contact with the porous semiconductor layer,
The coating unit, the dye-sensitized solar cell characterized by having a graded composition structure in which the degree of oxidation increases toward the side of the conductive metal portion on a side of the porous semiconductor layer. 2. The dye enhancement according to claim 1, wherein the covering portion is formed of an oxide of one or more kinds of corrosion-resistant metal materials selected from the group consisting of Ti, W, Ni, Pt, and Au. Sensitive solar cell. The conductive metal layer is a current collector disposed on the side of the porous semiconductor layer opposite to the side on which the substrate is provided, and the countless number for allowing the electrolyte to freely flow through the porous semiconductor layer The dye-sensitized solar cell according to claim 1 or 2, wherein a hole is formed in the conductive metal portion and is electrically connected to an external electrode, and the substrate is a transparent substrate. . The dye-sensitized solar cell according to claim 3 , wherein the conductive metal portion of the conductive metal layer is a mesh member . The conductive metal layer is a current collecting portion provided on the surface of the substrate, the conductive metal portion is provided on a side in contact with the substrate, and the covering metal portion is provided so as to cover the conductive metal portion. The dye-sensitized solar cell according to claim 1 , wherein the conductive substrate is a transparent substrate . It is a manufacturing method of the dye-sensitized solar cell of any one of Claims 1-5,
In the step of forming the covering portion on the conductive metal portion formed in advance, while introducing a small amount of a compound containing one or more elements selected from the group consisting of O, N, S, P, B and C A method for producing a dye-sensitized positive cell, wherein a gradient composition structure is formed by forming a conductive metal-coated raw metal film by a thin film technique . It is a manufacturing method of the dye-sensitized solar cell of any one of Claims 1-5,
In the step of forming a covering portion on a conductive metal portion that has been formed in advance, a gradient composition structure is provided by including a step of forming a sputter layer by a sputtering method and a step of forming a vapor deposition layer on the surface of the sputter layer by a vacuum vapor deposition method. A process for producing a dye-sensitized solar cell, characterized in that The method for producing a dye-sensitized solar cell according to claim 7 , wherein the vacuum deposition method is an arc plasma deposition method or a vacuum arc deposition method.

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